杨斜断裂以南元古代古侵入体的厘定及其地质意义

DETERMINATION OF THE PROTEROZOIC METAMORPHOSED INTRUSIVES TO THE SOUTH OF YANGXIE FRACTURE AND THE SIGNIFICANCE IN GEOLOGY

陕西商州杨斜断裂以南，天井湾断裂（商丹断裂带分枝断裂）以北地区发育的一套片麻杂岩体是中带（户县—兰田地区）秦岭岩群中解体出的最古老的变质侵入体，而秦岭岩群变质地层仅部分残留其中。依据侵入体产状、成分特点可进一步划分为4个岩石单元。岩石化学特征表明，该变质侵入体为典型的Ⅰ型花岗岩类，形成于洋壳向陆壳俯冲的构造环境，推断其形成时代为早晋宁期。

A suit of gneiss complex, which is distributed to the south of the Yangxie Fracture andthe north of the Tianjingwan Fracture (one of branchs of the Shangdan fault belt), is ascribed to the oldest metamorphosed intrusive disintegrated from the middle portion (in Huxian-Lantian area)of the Qinling rock suite. It contains some remnants from the metamorphosed strata of the Qinling rock suite. Four lithologic units can be identified according toattitudes of the intrusives. The characteristic lithochemistry indicates that the metamorphosed intrusive was formed under structural-collision environment between oceanic crustand continental crust. It is a typical Ⅰ-type granitoid.